A fuel vapor storage and recovery apparatus of the above-referred kind is for instance disclosed in WO 2010/032065 A1. This fuel vapor storage and recovery apparatus which is referred to as an adsorbent canister for control of emission for an automobile fuel tank comprises primary and secondary adsorbent beds and a flow passage configured to connect the adsorbent beds in series. The primary adsorbent bed encompasses/surrounds the secondary adsorbent bed. The primary adsorbent bed including a packed granular carbon is configured for flow end to end and has a polygonal, overall cylindrical sidewall, the secondary adsorbent bed being arranged in an internal passage of the canister extending from one end to another of the primary adsorbent bed, the secondary adsorbent bed being located in this internal flow passage. Between the primary and secondary adsorbent bed an airspace is defined which forms a kind of diffusion barrier between the primary and secondary adsorbent bed. The internal passage within the primary adsorbent bed is defined by a tube-like housing member which is sealed against a two-part cover fitted onto the top wall of the outer housing. This two-part cover includes a tank port, an atmospheric vent port and a purge port. The bottom of the carbon canister housing is sealed by an end cap including partitions which define a gas flow connection between the open ends of the primary and secondary adsorbent beds.
This design is rather compact and effective.
However, sealing of the inner tube defining the internal passage through the main carbon bed against the top wall of the carbon canister housing has to be achieved by a rubber seal or a similar sealing means. Moreover, mechanical interlocking between the inner tube and the outer housing has to be achieved somehow, for instance by a bajonet or locking nut.
To ensure leak tightness of the assembly during operation, there must, however, be conducted a quality insurance leak test to ensure the seal is not missing during preassembly or the seal is not damaged. Because the seal is quite small in cross-sectional area and rather large in diameter, assembly is quite difficult. Moreover, the seal takes valuable space in an area of the canister, where the canister design is critical.